Process for preparing cyclopropane



Patented May 6, i941 UNITE STAT i i? E 'FHCFL John M. Ort, Rockville Centre, N. Y., assignor to E. R. Squibb & Sons, New York, N. Y., a corporation of New York No Drawing Application June 23, 1939,

Serial No. 280,847

12 Claims. (Cl. 260-656) This invention relates tothe preparation of cyclopropane.

, Cyclopropane has heretofore been prepared by the treatment of trimethylene dihalides with metal reduction agents; e. g., by the reaction of trimethylene dibromide with zinc in about 86% ethanol (Lott and Christiansen,

Jour. A. Ph. A., '19 (1930) 341).

An improvement with respect to reaction time and yield has been obtained by efiecting the reduction of trimethylene dihalides in the presence of a catalyst consisting of a small proportion of a dissolved salt of a metal capable of being displaced by the metal reduction agent (as described and claimed in the copending application of W. A.'Lott, Serial No. 139,987, filed April 30, 1937, now Patent No. 2,211,787). The addition of the metal salt, however, results in an increase in the production of hydrogen (e. g., hydrogen may constitute l20% of the total evolved gas), and the excessive hydrogen evolution gives rise to mechanical difiiculties in the purification and recovery of cyclopropane. Cyclopropane is a gas (B. P. 34 C.) and the evolved gas mixture containing it is usually passed through a rectifying column to return vaporized alcohol, then through scrubbers into a refrigerated condenser to condense the cyclopropane. Non-condensable gases, such as hydrogen, interfere with the proper condensation of the alcohol, render the scrubbing less effective, interfere with the condensation of the cyclopropane, and decrease the yield of condensed cyclopropane.

It is the object of this invention to provide an improved process of preparing cyclopropane from trimethylene dibromide or trimethylene chlorobromide, in which the production of hydrogen is minimized.

It has been found that the production of hydrogen in the reaction of trimethylene dibromide or trimethylene chlorobromide with a metal re duction agent can be materially reduced, and

even substantially prevented, by effecting the reaction in the presence of a small proportion of an alkali, notably a substantially insoluble alkali such as Mg(Ol-I) z, and that, in addition, the alkali has a favorable influence on the cyclopropane-forming reaction itself. Furthermore, the presence of the alkali greatly diminishes the corrosion of the plant equipment by the acidic re- I action mixture.

The invention is applicable generally to processes for the production of cyclopropane by the reduction of trimethylene dibromide or tri methylene chlorobromide. Thus, the utilizable metal reduction agents include, inter alia, zinc and magnesium; and the reaction medium may range in composition from the conventional essentially alcoholic (lower aliphatic alcohol, e. g., methyl, ethyl, or isopropyl) to the essentially aqueous (i. e., media constituted in major proportion, or entirely, of water), as described and claimed in my copending application Serial No. 280,849 and the copending application of W. G. Christiansen, Serial No. 280,815 (now Patent No. 2,206,878), filed simultaneously herewith. The utilizable allzalies include, inter alia, NaOH, Ca(OE-I)2, NazCOs, and, notably, Mg(OH)z; and the utilizable catalysts include, inter alia, the especially advantageous dissolved salts of noble metals described and claimed in my copending application Serial No. 280,848, filed simultaneously herewith (now Patent No. 2,206,917).

The lVlg (OH) 2, for example, is preferably added in about 5 to 15% by weight of the reaction mixture, the optimum amount being dependent on the alcohol-water ratio in the reaction medium, the nature, and amount of the various catalysts present, and probably also on the operating temperature.

Alkalies substantially insoluble in the reaction mixture, e. g., Mg(O H) 2, are preferred, since they provide a reservoir of potential alkali capable of combining with acid without having'an initially-high OH-ion concentration.

The following examples are illustrative of the invention (the ingredients being mixed substantially in the given sequence, especially whennoble metal salts are used as catalysts) Example 1 A mixture of the following:

of Na-Br or KBr g is refluxed (about C.), and 62.4 g. trimethylene chlorobromide is added slowly so as to produce the desiredrate of evolution of cyclopropane; and about 98% yield is obtained, the evolved gases containing only 1.1% hydrogen.

Example 2 A mixture of the following: 95% ethanol cc 400 Distilled water cc 100 FeCl3 solution cc 8 I 5% CuSO4 solution cc 8 KBr g 3 Zinc dust g 75 Dry Mg(OH)2 g 70 is refluxed (about 80 C.) and 125 g. trimethylene chlorobromide is added slowly so as to produce the desired rate of evolution of cyclopropane; an 87% yield is obtained, the evolved gases containing 2.2% hydrogen.

Example 3 A mixture of the following:

Distilled water cc 165 KBr g--. l Acimul ,(a commercial mixture of glycerol stearates) g 6.24 5% FeCls solution cc 3 Zinc dust g 51.8 Dry Mg(OI-l) 2 g 20.0

is heated on the steam bath and 62.4 g. trimethylene chlorobromide is added slowly so as .to produce the desired rate of evolution of cyclopropane; an. approximately 75% yield is obtained.

Example 4 A mixture of the following: Distilled water oc 390 5% FeCla solution cc 8 KBr g 3 Acimul .'g 5 95% ethanol cc 50 Zinc dust g 65 5% Q1504 solution cc 8 Dry Mg(OI-l)2 g 70 is heated on the steam bath and 125g. trimethylene chlorobromide is added slowly so as is heated to about 80-90 C., and 128.2 g. trimethylene dibromide is added slowly so as to pro duce the desired rate of evolution of cyclopropane; an about 97% yield is obtained, the evolved gases containing about 1.5% hydrogen.

7 Example 6 A mixture of the following:

Water cc 120 5% FeCls solution cc 3 38% 'NaOl-I solution cc 60 KBr 1 Powdered zinc g 51.8

'is heated on a steam bath, and 62.4 g. trimethylene chlorobromide is added fast enough to produce a smooth and even evolution of cyclopro- Example 7 Substitution of g. Ca(OH)z for the NaOH in the preceding example (total H2O to be 200 cc.)

gives an eflicient production of cyclopropane rel-' atively low in hydrogen content.

is heated in a steam bath and 128.2 g. trimethylene dibromide is added slowly so as to produce the desired rate of evolution of cyclopropane;

an about 95% yield is obtained, the evolved gases containing a little over 5% hydrogen.

Example 9 A mixture of the following: Distilled water cc 400 95% ethanol cc 40 Zinc dust V 200 Aqueous AgNO3 solution containing 0.0.175 g.

AgNOg cc 335 NaBr g 8 Dry Mg(OI-I)' g pane; an about 87% yield is obtained, the evolved gases containing 6% hydrogen.

lowed for this additionto insure'uniform distribution of the catalyst.

Example 10 A plant-scale production of cyclopropane is carried out as follows: 90 gallons of distilled water and 240 pounds of zinc dust are placed in a jacketed, internally zinc-coated still and brisk- 1y agitated; then 74 g. of AgNoz dissolved in 25 gallons of distilled water is added gradually to the swirling contents in the still, and then 10 pounds of NaBr is added and dissolved, followed by 45 pounds dry Mg(OH)2 and 8 gallons of ethanol; the still is then closed and steam admitted to the jacket until the temperature of the reaction mixture reaches about 50 C., whereupon the steam is cut off and the slow addition of 400 pounds of trimethylene chlorobromide begun; the reaction being exothermic, cold water is passed into the jacket to prevent the temperature rising above 60 C., and the rate of addition of the chlorobromide is increased periodically until it reaches about pounds per hour. The evolved cyclopropane is recovered in over 83% yield with a low hydrogen content.

The residue in the still is filtered while still.

warm in order to get the filtrate for bromine recovery, the filtration proceeding smoothly and rapidly despite the presence of Zn(OH)z and some Mg(OH)2. The Mg(OH)2 in addition greatly reduces the acidity of the reaction mixture and hence also reduces the corrosion of the plant equipment.

The invention may be variously otherwise embodied within the scope of the appended claims.

I claim:

' 1. The process of preparing cyclopropane which comprises reacting a compound of the group consisting of trimethylene dibromide and trimethylene chlorobromide with a metal reduc tion agent in the presence of an alkali.

2. The process of preparing cyclopropane which comprises reacting a compound of the group consisting of trimethylene dibromide and trimethylene chlorobromide with a metal reduction agent in the presence of Mg(OH) 2.

3. The process of preparing cyclopropane which comprises reacting a compound of the group consisting of trimethylene dibromide and trimethylene chlorobromide with a metal reduction agent in the presence of 5 to 15% of Mg(OH)2.

4. The process of preparing cyclopropane which comprises reacting trimethylene dibromide with zinc in the presence of an alkali.

5. The process of preparing cyclopropane which comprises reacting trimethylene chlorobromide with zinc in the presence of an alkali.

6. The process of preparing cyclopropane which comprises reacting a compound of the group consisting of trimethylene dibromide and trimethylene chlorobromide with zinc in an aqueous lower-aliphatic-alcohol medium in the presence of an alkali.

7. The process of preparing cyclopropane which comprises reacting a compound of the group consisting of trimethylene dibromide and trimethylene chlorobromide with zinc in an aque ous ethanol medium in the presence of Mg(OH)z.

8. The process of preparing cyclopropane which comprises reacting a compound of the group consisting of trimethylene dibromide and trimethylene chlorobrcmide with a metal reduction agent in the presence of an alkali and of a dissolved salt of a metal capable of being displaced by the metal reduction agent.

9. The process of preparing cyclopropane which comprises reacting a compound of the group consisting of trimethylene dibromide and trimethylene chlorobromide with a metal reduction agent in the presence of Mg(OH)z and o! a dissolved salt of a metal capable of being displaced by the metal reduction agent.

10. The process of preparing cyclopropane which comprises reacting a compound of the group consisting of trimethylene dibromide and trimethylene chlorobromide with a metal reduction agent in an aqueous lower-aliphatic-alcohol medium in the presence of an alkali and of a dissolved salt of a metal capable of being displaced by the metal reduction agent.

11. The process of which comprises reacting a compound of the group consisting of trimethylene dibromide and trimethylene chlorobromide with zinc in the presence of Mg(OH)z and of a dissolved salt of a metal capable of being displaced by zinc.

12. The process of preparing cyclopropane which comprises reacting a. compound of the group consisting of trimethylene dibromide and trimethylene chlorobromide with zinc in aqueous ethanol, in the presence of Mg(OH)2 and of a dissolved salt of a metal capable of being displaced by zinc.

JOHN M. ORT.

preparing cyclopropane' 

